B+M+W=G. I’m not one for mathematical equations, but what if I told you that the initials BMW added up to the new green car and that it had actually beaten out the Toyota Prius in a 545 mile London-Geneva run?

I hope you placed your bets, because the results are in.

Two reporters for London’s Sunday Times decided to put the efficiency of these two cars to the test. In the end, while the BMW Midsize 5 Series Sedan (520d) won by a nose, beating the Prius – which is 570 lbs. lighter! — by 0.9 mpg, the implications of the victory were more of a landslide.

The Prius is classified by the American government as the “most fuel-efficient car sold in the U.S.” and Toyota has used this acknowledgement to sell over a million vehicles since its launch in 1997.

Disclaimer: if you’re one of those customers, you may not want to read on!

It’s true the Prius has become a status symbol of environmentally conscious buyers and has enjoyed loads of publicity from celebrities like Leonardo DiCaprio — not to mention VIP treatment as the only car allowed to drive in carpool lanes without additional passengers and provide tax benefits. But this car, touted as the most fuel efficient car ever made, seems to have finally met its match, and from an unlikely competitor — an Autobahn-inspired performance machine!

Suddenly Hybrid has a new rival — Efficient Dynamics.

Efficient Dynamics is the fuel-saving technology BMW says is responsible for its victory. Its features include the new four cylinder engine, brake regenerative system, better aerodynamics to reduce drag, low rolling resistance tires, a continuous fuel consumption gauge on the dashboard and a six-speed manual transmission. Rather than betting it all on one new technology like the Prius (powered by its petrol-electric drivetrain), BMW made a number of refinements that, when working together, apparently make for a drastic improvement in efficiency. Didn’t your mother ever tell you not to put all of your eggs in one basket?

I must admit though, before rushing out to BMW of Beverly Hills, two main concerns crossed my mind. First, the Prius is a car known for its high performance in urban conditions, perfect for cities like L.A. and London. With that said, I have to question the validity of a race that included over 200 miles of highway driving. However, in its defense, the race also covered at least 200 miles of B roads, including winding ascents (where the Prius struggled to maintain speed) — and over 100 miles of urban driving was added into the usual direct route.

One other factor that can’t be ignored is that the BMW’s price tag is considerably higher than the Prius and its diesel gas is more costly at the pump — a mathematical equation you don’t have to be a genius to figure out. But when the race was over, the BMW still had one-third of its tank of gas, while the Prius had to stop for more. So, maybe the math isn’t that simple.

For now, the Prius may remain top dog in the public’s mind when they think of an affordable pump-avoidance vehicle. But the BMW’s performance arises the question of whether hybrid technology truly will be the fuel for the future. BMW’s new four-door hatchback, the 118d — which was released in Europe and employs Efficient Dynamics — was also awarded the 2008 World Green Car award this past week, adding further insult to hybrid technology’s injury.

It seems to me this race only scratched the surface in the competition for the most efficient technology for future drivers. So, as they say at the races — place your bets and let the games begin!